Spire hoisted atop New York’s One World Trade Center

The final section of the spire that will top off One World Trade Center is raised past iron workers to the top of the building in New York, May 2, 2013. The piece will be attached at a later date.

NEW YORK — Crane operators hoisted the final pieces of the spire atop One World Trade Center on Thursday, helping to fill the void in the New York City skyline that was left by the attacks of Sept. 11, 2001.

When complete — a beacon is still to be installed — the tower will stand 1,776 feet high, making it the tallest building in the Western Hemisphere.

Ironworkers will finish installing the spire, which weighs about 800 tons and is 400 feet tall, at a later date.

The tower is one of four skyscrapers designed to rise around the footprints of the fallen Twin Towers in a partnership between developer Larry Silverstein and the Port Authority of New York and New Jersey, which owns the site.

The footprints of the fallen towers have been turned into a memorial to the nearly 3,000 people killed in the 2001 attacks by al Qaeda hijackers.

One World Trade Center, formerly called the Freedom Tower, is estimated to cost more than $3 billion and is due to open next year. It will have 3 million square feet of office space, an observation deck, shops and restaurants.